Commonwealth of Massachusetts v. Nathaniel Jennison was a decisive court case in Massachusetts in 1783 which effectively abolished slavery in that state. It was the third in a series of cases which became known as the Quock Walker cases.
Nathaniel Jennison was arrested for beating Quock Walker and indicted on a criminal charge of assault and battery in September 1781. The trial before the Supreme Judicial Court of Massachusetts was held in April 1783. Jennison's defense was that Walker was a runaway slave but Walker countered that the Massachusetts Constitution had made slavery illegal in 1780. Chief Justice William Cushing accepted this argument and directed the jury that the issue of whether Walker had been freed or not was irrelevant because slavery was no longer constitutional. The jury convicted Jennison who was fined forty shillings.
The case was not widely publicized but it made it clear that the law would not defend the property rights of slave-owners. Slavery (or the willingness to reveal its presence) declined so that, by the time of the 1790 census, no slaves were recorded in this state.